FEM creep damage study for nickel-base single crystal structure under multiaxial stress conditions

Based on the microstructural assessment, a two-state-variable crystallographic creep damage constitutive equation was presented for nickel-base single crystal superalloys, which takes into consideration of the rafting-derafting and the damage of the voids simultaneously. The constitutive equation was programmed as a user subroutine umat into the ABAQUS. With the uniaxial creep experimental data, the constitutive equation can model the creep damage behavior of nickel-base single crystal superalloys, especially the dependence of the creep anisotropy on the crystallographic orientation. The double shear specimens and modeling blades were studied experimentally to validate the constitutive equation. The results of the validation are satisfactory. The damage and life behaviors of a turbine blades were presented as an example of the application. The influence of the crystallographic orientations on the blade life was analyzed specially for the optimization of blade crystallographic orientations. The optimization of the crystallographic orientations will find a maximum-life orientation.